Field of the Invention
The present invention relates to the field of computer imaging and more particularly to three-dimensional visualization of object volumes.
Description of the Related Art
Computer imaging, synonymously referred to as digital imaging, is a field of computer science relating to the acquisition and manipulation of digital imagery. In the study and practice of computer imaging, images can be acquired either directly (being the data acquired from one or more sensors), or acquired indirectly (being produced through a computed transformation of the acquired sensor data), and stored digitally in memory. The images can be stored in raster form as bitmapped graphics, or in vector form through one or more representative expressions. Once stored, images can be manipulated to enhance the images or to derive new images. Computer imaging generally encompasses a wide field of application ranging from design and computer graphics, to medical systems, to machine vision. Computer imaging has particular application to medical imaging though other emerging fields include imaging of cargo and vehicles for homeland security.
Three-dimensional (3D) visualization is a part of computer imaging the refers to the rendering of real world 3D objects into some form of computerized 3D representation, whether it be projected on a two-dimensional (2D) computer screen, or viewed through immersive virtual reality equipment. Volume visualization is a form of 3D visualization where physical objects modeled in 3D can be studied and examined in greater detail and the modeled objects further can be manipulated in order to, for example, provide visual confirmation of the content of a visualized volume, test scientific hypotheses in relation to a visualized volume, to simulate a process relating to the visualized volume, or to practice a medical procedure on a portion of the visualized volume. Current applications of this type include medical imaging, surgical teaching and planning, geophysical sensing, homeland security and weather modeling.
Volume visualization is widely-used in biomedical imaging for displaying of 3D volumetric images of object volumes. In the case of tomographic imaging including positron emission tomography (PET) scanning, computed axial tomography (CT) and X-ray tomography, and also Magnetic Resonance Imaging (MRI), volume visualization is used in applications such as cancer diagnosis, magnetic resonance angiography imaging (MRA) and other cardiac and neurological vasculature imaging, the evaluation of breast implant morphology, and magnetic resonance cholangiopancreatography. Currently, the time-consuming, computationally intensive processing that is required for MRI and tomographic volumetric visualization severely limits its practical and clinical application. In addition, the problem is exacerbated by the growing size of MRI and tomographic images, resulting from on-going improvements in the resolution of MRI and tomographic scanners.
For volume visualization on standard 2D computer displays, two major imaging techniques include Maximum Intensity Projection (MIP) and Volume Rendering (VR). The three basic steps common to both techniques include first the reconstruction of images from acquired sensor data, second the computation of a set of 2D projections of the 3D sensor data, and third a graphical display of a “movie”, where each frame is a 2D projection image, giving the viewer the perception of a rotating 3D object on the 2D screen. In as much as the images acquired from sensor data must be reconstructed, both methods are known to be computationally expensive. Furthermore, as both methods are lossy in nature, the addition of image reconstruction noise cannot be avoided, resulting in low quality 2D projection images, which in turn result in low quality visualizations.